Tory MPs raged at two sets of European judges this week. In one case at least, Britain is pondering a big repatriation of powers

“SACK the lot of them” came a cry from the Conservative benches of the House of Commons on February 7th, backed by a rumbling chorus of “disgrace” and “shame”. The object of the backbenchers' ire was the European Court of Human Rights in Strasbourg. Its judges had sorely provoked Parliament—not to mention the press and public opinion—by preventing Britain from deporting a radical Muslim cleric, Abu Qatada, to his native Jordan, citing concerns that evidence obtained by torture might be used against him there. That had led a British judge to grant him bail, albeit with strict curbs on his movements. No matter that Theresa May, the home secretary, calls the cleric a serious threat to national security.

Some Conservative MPs urged Mrs May to defy the court in Strasbourg, the judicial arm of the 47-member Council of Europe and guardian of the European Convention on Human Rights (ECHR). Others want her to go further and suspend recognition of the convention, a rights charter crafted soon after the second world war. Such calls are in vain. Lib Dem ministers, backed by two liberal-minded Conservatives—Ken Clarke, the justice secretary, and Dominic Grieve, the attorney-general—have ruled out any British exit from the ECHR. In the short term, the government hopes assurances from Jordan may allow for Mr Qatada's deportation. More broadly, the coalition is trying to reform the Strasbourg court and make it defer to national decisions more often.

Conservative MPs also launched a parallel assault on a second outfit, the European Court of Justice (ECJ) in Luxembourg, the highest court of the European Union. This caused less fuss. But it is likely to prove more explosive in the end than heckles about sacking Strasbourg justices.

The reason is an obscure wrinkle of treaty law, linked to a European ambush of the previous Labour government. In 2007 the EU was poised to transfer a thicket of crime-fighting and policing laws from one section of the union's treaties (in which individual countries have national vetoes and ECJ judges may not meddle) to a section of the treaties governed by majority voting and ECJ oversight. The laws at stake include the most ambitious EU experiments in the field of law enforcement. One is the European Arrest Warrant, a powerful tool that allows judges anywhere in the union to have suspects arrested in another country at their say-so. The warrant offers only limited rights to mount an appeal against extradition.

When Labour ministers sought concessions to answer concerns about the ECJ having a final say over such measures, other governments led by France and Germany retaliated by offering Britain an alternative: a one-off, time-limited right to opt out of all the crime-fighting measures or sign up to all of them for ever. In diplomatic jargon, Britain was offered a “nuclear button” to push.

The deadline for a British decision falls in 2014. But on February 6th fully 102 Tory MPs urged the government in an open letter to seize the moment, and opt out of the lot. This was no empty grandstanding. Though the question is set to strain coalition unity (Lib Dems instinctively like pan-European co-operation) ministers have told officials seriously to weigh the case for and against an opt-out.

In 2007 it was assumed that no British government would ever want to withdraw from all the measures. In addition to the arrest warrant, they cover uncontroversial things like Britain's membership of EU systems for cross-border policing and prosecutorial co-operation, as well as easier access to national criminal record registers around Europe. But the political landscape has changed. Tory MPs are in their most Eurosceptic mood ever, and are keen for the government to repatriate powers from Brussels. And, despite assurances that the European Arrest Warrant would be reserved for the gravest crimes, it has been used thousands of times in cases both footling (one extradition involved the alleged theft of a piglet) and troubling (warrants have swept up people tried in absentia without their knowledge).

The issue will not go away. In January 2011, during a big fight in Westminster over EU powers, the government offered a concession to Eurosceptics: a promise of a vote in Parliament on whether to opt out of justice and policing laws. Most Tories would probably vote to walk away, putting both their Lib Dem allies and the opposition Labour Party on the spot. Would they want to defend unpopular Euro-judges by voting for a big increase in their powers?

Not everyone wants out. Police chiefs and some in the Home Office like tools such as the European Arrest Warrant. They cite a 2005 case when the warrant was used to extradite a man accused of involvement in the London Underground bomb plots to Britain from Italy within days, when it might have taken a year under previous rules. Even Eurosceptics who want to use the opt-out are in favour of preserving some forms of EU co-operation, such as criminal-record checks. Such sceptics insist that Britain, having walked away, will be at liberty to ask to opt back in to things it likes. Surely, they argue, other European powers would not reject such requests.

They may be too confident. A junior Home Office minister, James Brokenshire, predicted last year that the European Commission “would attach conditions” to any British requests for selective re-entry, perhaps insisting that Britain join bundles of related measures. Negotiations could become bound up with unrelated horse-trading, perhaps over the EU budget. Inside the coalition, Lib Dems may have to choose between their pro-European instincts and their commitment to civil liberties.

The 2014 opt-out deadline was “always a time-bomb” waiting to be discovered by British MPs, says a Brussels official. They have found it now. In the next couple of years, the bomb will either be defused or detonated.